1. Field of the Invention
The present invention relates to a method of producing granular sodium dichloroisocyanurate from the wet cake thereof obtained in the manufacturing process.
Sodium dichloroisocyanurate has been widely used as a solid chlorine compound which is effective to release active chlorine for various purposes such as for sterilizing water in swimming pools and dirty water such as, for instance, sewerage.
2. Description of the Prior Art
For storage, transportation and use, it is preferable to supply sodium dichloroisocyanurate in the form of granules.
Prior art methods for producing granular sodium dichloroisocyanurate have been disclosed in Japanese Pat. No. 513 484 (Jap. Pat. Publn No. 23 198/1967) granted to the assignee of the present patent application, wherein chloroisocyanuric acid or an alkali metal thereof containing an adjusted amount of water is formed into tablets with a surface pressure of about 1,000 Kg/cm.sup.2. The tablets are then crushed. In U.S. Pat. No. 3,886,249 sodium dichloroisocyanurate powder containing an adjusted amount of water for hydration is fed to compactor rolls to form a sheet thereof and the resulting sheet is broken into granules.
The method disclosed in the Japanese patent has the disadvantage that the wet or moisture containing acid or salt has a relatively high viscosity or stickiness which adversely affects the ability to continuously supply it in fixed amounts to a pellet forming machine. In addition, when the tablets are crushed in a granulator to produce uneven dimensional agglomerates, considerable pulverization accompanies the process. Therefore, this method is not suitable for industrially preparing commercial products.
The method of the United States patent has the disadvantage that the sodium dichloroisocyanurate powder containing hydration water is so sticky that it is difficult to continuously supply the material in a fixed amount through a hopper to the sheet forming compactor, because of a so-called "bridging" phenomenon in the hopper which, in turn, produces blocking or jamming. Such blocking or jamming may also cause loss of hydration water due to friction heat and consequently permit chain-reactional thermal decomposition of the sodium dichloroisocyanurate. This method is, therefore, also not suitable for safe and smooth production of the granules on an industrial scale.